Water Hammer Control Using Additional Branched HDPE Pipe

In pressurised pipeline systems, various water hammer events commonly occur. This phenomenon can cause extensive damage or even lead to a failure of the pumping system. The aim of this work is to experimentally re-examine the possibility of using an additional polymeric pipe, installed at the downstream end of the main pipeline, to control water hammer. A previous study on this topic investigated additional polymeric pipes connected to the hydraulic system with a short joint section of the same diameter as the main pipeline. In the current research, a different method of including an additional pipe was considered which involved connecting it with a pipe of a smaller diameter than the main pipeline. Three additional HDPE pipes, with different volumes, were investigated. The performance of the devices was studied for hydraulic transients induced by both rapid and slow, manual valve closures. Experimental results show that the additional polymeric pipe can provide significant pressure surge damping during rapid water hammer events. As the valve closing time lengthens, the influence of the additional pipe on the maximum pressure increase is reduced. The additional HDPE pipe does not provide notable protection against hydraulic transients induced by slow valve closure in terms of reducing the first pressure peak. No relationship between the volume of the additional pipe and the damping properties was noticed. The observed pressure oscillations were used to evaluate a one-dimensional numerical model, in which an additional pipe is described as a lumped parameter of the system. The viscoelastic properties of the device were included using the one element Kelvin–Voigt model. Transient flow equations were solved with the implicit method of characteristics. Calculation results demonstrate that this approach allows one to reasonably reproduce unsteady flow oscillations registered during experiments in terms of the maximum pressure increase and pressure wave oscillation period.